The titles says it all. I would like to buy a SIM cart to enable mobile Internet on my phone in all of Portugal, preferably for a month. Is this possible, or is mobile internet only for local residents?

We just came back. We bought NOS sim card. The first and only time in Portugal we felt we were robbed!! 10 hours card was finished after 2 hours. When we complained they finally confessed that itws not really 10 hours. We spent over 50 euro for a week!!
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user22127Oct 28 '14 at 19:01

Phone IX - you can find them in every post office shop; it belongs to the post office company.

Lyca Mobile - kind of new. It's widely available and aparently with good prices.

ZON telemovel - it's part of a cable tv group; in principle a good solution but only if you subscribe to cable

Vectone Mobile A very recent virtual operator, currently offering Internet when you top up.

Recharging a pre-paid simcard in Portugal, for someone from abraod, can be a problem since the most common way of doing it is in ATM machines. You probably can't recharge your phone with a foreign ATM card since you only get a small set of operations. The alternative way is to go to the physical shop where you bought the card (or another one from that network) or go to any shop with "payshop". You can find a near by agent here PayShop (only pt).